JPH11283874A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrolytic capacitor with high breakdown voltage, which has superior impedance characteristics, leakage current and reliability. SOLUTION: This electrolytic capacitor has a constitution using a capacitor element 12, which has an anode foil 1 comprising a valve-action metal in which a dielectric surface oxide film is formed on the surface, a cathode foil 3, solid organic conducting material 2 formed between the anode foil 1 and the cathode foil 3 and driving an electrolyte solution 10. Thus, the electrolytic capacitor at the high withstand voltage having the excellent impedance characteristics, leakage current and reliability can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high withstand voltage electrolytic capacitor having excellent impedance characteristics, leakage current characteristics and reliability by using a solid organic conductive material and a driving electrolyte together.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been digitized and operated at higher frequencies, there has been a demand for electrolytic capacitors, which are electronic components, which have larger capacities than conventional products and have excellent impedance characteristics in a high frequency range. In order to meet such demands, the conductivity of a driving electrolyte (hereinafter referred to as an electrolyte) is improved, the resistance of a separator is reduced, or a sheet insulator such as paper, cloth, nonwoven fabric or a polymer film is used. Many attempts have been made to use a conductive composite obtained by conducting as a separator.

[0003] In addition, attempts to make the separator conductive include weaving or mixing carbon fibers or particles,
Alternatively, a method such as compounding with graphite powder has been proposed. Furthermore, a method is disclosed in which a conductive polymer is formed on the surface by chemical oxidation polymerization from a monomer of pyrrole, thiophene, or aniline (Japanese Patent Application Laid-Open No. Sho 64).
-90517).

[0004]

However, in the above-mentioned conventional structure, there is a limit to the improvement of the conductivity of the electrolytic solution, and the conductivity is as high as 10 to several tens mS / cm as of today.
And an electrolytic solution having a sufficient conductivity has not yet been obtained, and an electrolytic solution type electrolytic capacitor having a sufficient impedance characteristic has not been obtained.

On the other hand, efforts to reduce the resistance of the separator include reducing the thickness of the separator, reducing the density, making the opening diameter uniform, or changing from paper to a polymer nonwoven fabric. Due to problems such as insufficient strength due to
The effect of lowering the resistance has not yet been obtained.

[0006] Further, the separator made conductive by weaving or mixing carbon fibers or particles has a problem that the electric conductivity is still insufficient and it is difficult to obtain a separator having a low density. Further, when a separator composited with graphite powder is used, there is a problem that the graphite powder drops off and the short-circuit increases due to dispersion in the electrolytic solution.

On the other hand, in a method of forming a conductive polymer on the surface by chemical oxidation polymerization from a monomer of pyrrole, thiophene, or aniline, the influence of the oxidizing agent on the deterioration of the dielectric oxide film and the formation of the conductive polymer It is difficult to construct an electrolytic capacitor having a rated voltage exceeding 35 V because there is almost no (capacity for repairing a defective portion of a dielectric oxide film). In some cases, an increase in leakage current or a short circuit between the anode and the cathode may occur.

The present invention solves such a conventional problem,
An object of the present invention is to provide a high withstand voltage electrolytic capacitor having excellent impedance characteristics, leakage current characteristics, and reliability.

[0009]

In order to solve the above-mentioned problems, an electrolytic capacitor according to the present invention comprises: an anode made of a valve metal having a dielectric oxide film formed on a surface; a cathode; And a capacitor element made of a solid organic conductive material and a driving electrolytic solution provided in the above. According to the present invention, it is possible to obtain an electrolytic capacitor having excellent withstand voltage characteristics, leakage current characteristics, and high withstand voltage.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention relates to an anode foil made of a valve metal having a dielectric oxide film formed on a surface thereof, a cathode foil, and an anode foil and a cathode foil. A capacitor element made of a solid organic conductive material provided in the above, a bottomed cylindrical metal case for accommodating the capacitor element together with the electrolytic solution, and a sealing member for sealing an opening of the metal case. It is. According to this configuration,
By utilizing the high electrical conductivity of the solid organic conductive material, the resistance between the electrodes can be significantly reduced in the conductive portion, and as a result, an electrolytic capacitor having excellent impedance characteristics can be easily obtained, and at the same time, the valve action metal By interposing an electrolyte having a capability of repairing the dielectric oxide film, an electrolytic capacitor having high withstand voltage and low leakage current can be formed.

According to a second aspect of the present invention, in the first aspect, the solid organic conductive material is an organic semiconductor, and more specifically, the organic semiconductor is 7,7,8,8, tetracyanoquinodimethane. Complex and a derivative thereof (hereinafter, referred to as TCNQ complexes).
By melting and impregnating the CNQ complexes, the layer of the solid organic conductive material having high conductivity can be sufficiently filled into the pits of the etched anode.
In particular, an electrolytic capacitor having excellent impedance characteristics can be obtained even in a high frequency region of 100 kHz or more. Furthermore,
A TCNQ complex is directly applied to a separator substrate, or a capacitor element in which an anode foil and a cathode foil are wound through a separator substrate, or one or two or more anode and cathode layers are laminated through a separator substrate. Since the capacitor element can be easily impregnated with a heated and melted TCNQ solution and then solidified by cooling, conductivity can be easily developed.
This has the effect that an electrolytic capacitor having excellent impedance characteristics can be easily obtained.

According to a fourth aspect of the present invention, in the second aspect, the conductive polymer is pyrrole, aniline, thiophene, ethylenedioxythiophene, sulfonated aniline, sulfonated pyrrole, sulfonated thiophene. A polymer of sulfonated ethylenedioxythiophene and their derivatives (hereinafter collectively referred to as polymerizable monomers) (Claim 4), and a method for forming the polymer by a liquid phase chemical polymerization; A method using gas phase chemical polymerization, a method using liquid phase-electrolytic polymerization, a method using a residual polymer by drying a soluble polymer solution (Claim 5)
Further, the resulting conductive polymer is made of polypyrrole, polyethylenedioxythiophene, polyaniline, polypyrrole formed by electrolytic polymerization, polypyrrole formed by electrolytic polymerization, polyethylenedioxythiophene by the combination of the most suitable material-polymerization method. , Polyaniline, and a dried residue sulfonated polyaniline obtained by drying a solution of a soluble polyaniline (claim 6). According to this configuration, in the case of liquid phase polymerization, the capacitor element is immersed and polymerized in a solution containing at least the polymerizable monomer and an appropriate oxidizing agent, and in the case of electrolytic polymerization, at least the polymerizable monomer and In the case of gas phase polymerization, the capacitor element is immersed in a solution containing an appropriate oxidizing agent, and is subjected to polymerization. By installing a capacitor element in the gas phase containing at least the polymerizable monomer,
Since the layer of the solid organic conductive material having high conductivity can be sufficiently filled into the pits of the etched anode, an electrolytic capacitor having excellent impedance characteristics can be obtained even in a high frequency region of 100 kHz or more. Furthermore, since the conductive polymer can be easily expressed by vapor-phase polymerization of the conductive polymer directly to the separator substrate or the anode or the cathode, an electrolytic capacitor having excellent impedance characteristics can be easily obtained. .

In addition, since these conductive polymers have high compatibility with an electrolyte mainly composed of an organic substance, when they are impregnated with the electrolyte, they quickly swell into the inside of the conductive polymer. -It can diffuse, so that even when a capacitor element having a dielectric oxide film covered with a conductive polymer is formed, the ability to repair the dielectric oxide film can be maintained at a high level.

According to a seventh aspect of the present invention, there is provided a method according to any one of the first to sixth aspects, wherein an organic acid salt and an inorganic salt are added to an organic solvent capable of swelling the electrolyte by immersing the electrolyte in an organic conductive material. This is an electrolytic solution in which an acid salt is dissolved.
According to this configuration, as described above, the electrolytic solution can quickly swell and diffuse into the conductive polymer,
Even when a capacitor element in which a dielectric oxide film is covered with a conductive polymer is formed, it has an effect that the ability to repair the dielectric oxide film can be kept high.

The invention according to claim 8 is the invention according to claim 7, wherein the concentration of the base or the hydroxide of the base in the electrolyte constituting the electrolyte is 1% by weight. When the measurement temperature is 30 ° C., the hydrogen ion concentration in the aqueous solution of the base or the hydroxide of the base is 1.
It is a composition using a compound having 0 × 10 ⁻¹³ mol / dm ³ or more, and specific examples thereof include a compound having an alkyl-substituted amidine group as a base constituting an electrolyte, and a compound having an alkyl-substituted amidine group. The electrolytic capacitor is limited to at least one selected from the group consisting of quaternary salts, tertiary amines, and ammonium. According to this configuration,
This has the effect that a capacitor having less reliability problems such as leakage of the electrolyte can be formed.

The hydrogen ion concentration is 1.0 × 10 ^-13
When an electrolytic solution comprising an electrolyte of a strongly basic base (e.g., tetraalkylammonium or tetraalkylphosphonium) of less than mol / dm < ³ > is used, when the capacitor is configured in the configuration of the present invention, the electrolyte is used in a high-temperature / high-humidity complex environment (e. ℃-
In a long-term test at 95% RH), the sealing member is easily damaged by the influence of a strongly basic base, and as a result, liquid leakage is likely to occur, so that reliability is not practically sufficient. Is not preferred.

According to a ninth aspect of the present invention, in the invention according to the eighth aspect, the base constituting the electrolyte is a compound having an alkyl-substituted amidine group, a quaternary salt of a compound having an alkyl-substituted amidine group, or a tertiary amine. , Ammonium, and at least one selected from the group consisting of ammonium, and each of these electrolytes has a base or a base hydroxide at a concentration of 1% by weight and a measurement temperature of 30 ° C. Since the hydrogen ion concentration in the aqueous solution of the hydroxide is 1.0 × 10 ⁻¹³ mol / dm ³ or more, it has an effect that the above-described liquid leakage due to the strong basicity hardly occurs.

According to a tenth aspect, in the ninth aspect, the quaternary salt of the compound having an alkyl-substituted amidine group is quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms. And at least one selected from the group consisting of an imidazole compound, a benzimidazole compound, and an alicyclic amidine compound. According to this configuration, when hydroxide ions are generated by the electrolysis reaction in the electrolytic solution, the reaction rate of the reaction between the hydroxide ions and the amidine group of N—C—N is high. Therefore, the electrolytic product can be quickly eliminated, and as a result, there is an effect that leakage of the electrolytic solution to the outside can be prevented even under high temperature and high humidity.

The invention according to claim 11 is the invention according to claim 10, wherein the quaternary salt of the compound having an alkyl-substituted amidine group is 1-methyl-1,8-diazabicyclo [5,4,0] undecene. -7, 1-methyl-1,5-
Diazabicyclo [4,3,0] nonene-5,1,2,3
-Trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2
-Ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(-
3 'heptyl) imidazolinium, 1,3-dimethyl-
2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,
This is a configuration using at least one selected from 3-dimethylimidazolium, 1-methyl-3-ethyl-imidazolium, and 1,3-dimethylbenzimidazolium. According to this configuration, the conductivity of the electrolyte can be increased, and the heat resistance is excellent, so that the electrolyte can be prevented from leaking to the outside under high temperature and high humidity, and the high temperature stability can be maintained. And an electrolytic capacitor having excellent impedance and low impedance can be provided.

According to a twelfth aspect of the present invention, in the eleventh aspect, the solvent of the electrolytic solution has a boiling point of 200 ° C. or more and the conductivity of the electrolytic solution at a measuring temperature of 30 ° C. is 1.0 mS / cm. And the spark generation voltage is 80V
The configuration is as described above. According to this configuration, an external appearance due to an increase in internal pressure of the capacitor caused by heat treatment during surface mounting (the capacitor is also exposed to a high temperature together with the substrate for soldering) which is a problem of the surface mounting electrolytic capacitor. Deformation and poor soldering during mounting due to the high boiling point (low vapor pressure) of the electrolyte solvent, and the high conductivity ensures impedance performance and the spark generation voltage Is sufficiently high, so that an electrolytic capacitor having a high withstand voltage can be formed.

In a group electrolytic capacitor for surface mounting in which a sealing member is formed by using an elastic rubber, an electrode foil of a capacitor element, a separator, a solid electrolyte, and the inner surface of a case or the adsorbed moisture contained in a rubber sealing member. The adsorbed moisture and the like adhering to the surface are vaporized at a high temperature at the time of surface mounting, and the pressure inside the capacitor rises remarkably, resulting in poor airtightness of the capacitor and popping out of the sealing member, but with a high boiling point (vapor pressure (Low) The total pressure inside the capacitor at the time of mounting can be reduced by incorporating an electrolytic solution using a solvent. Therefore, it is preferable to include a liquid component (here, an electrolytic solution) in addition to the solid electrolyte type electrolyte, because it is possible to suppress an increase in pressure inside the capacitor and to improve poor soldering and the like.

Examples of the electrolyte solvent having a boiling point of 200 ° C. or higher include 3-alkyl-1,3-oxazolidine-2-yl.
ON (more specifically, 3-methyl-1,3-oxazolidin-2-one: boiling point: 260 ° C.), 1,3-dialkyl-2 other than 1,3-dimethyl-2-imidazolidinone
-Imidazolidinone (more specifically, 1,3-dimethyl-2-imidazolidinone: boiling point 236 ° C, 1,3-dipropyl-2-imidazolidinone: boiling point 255 ° C, 1-
Methyl-3-ethyl-2-imidazolidinone: boiling point 23
0 ° C), 1,3,4-trialkyl-2-imidazolidinone (more specifically, 1,3,4-trimethyl-2-
Imidazolidinone: boiling point 241 ° C), 1,3,4,5-
Tetraalkyl-2-imidazolidinone (more specifically, 1,3,4,5-tetramethyl-2-imidazolidinone: boiling point 249 ° C.), cyclic lactone (more specifically, γ-butyrolactone: Polyhydric alcohol (more specifically, ethylene glycol: boiling point 20)
1 ° C., glycerin: boiling point 290 ° C.), carbonate (more specifically, ethylene carbonate: boiling point 238 ° C., propylene carbonate: boiling point 242 ° C.) and the like.

Next, specific embodiments of the present invention and a conventional example as a comparative example will be described with reference to the accompanying drawings.

FIGS. 1 (a) and 1 (b) are a partial cross-sectional perspective view showing the structure of the electrolytic capacitor of the present invention and a conceptual diagram in which main parts of the element are enlarged. In FIG. After the surface is roughened, a dielectric oxide film 11 is formed by an oxidation treatment, and an anode foil 1 made of an aluminum foil having a solid organic conductive material 2 formed on the surface thereof and a cathode foil 3 formed by etching the aluminum foil The surface of the dielectric oxide film 1 is wound by a separator 4 or roughened by an etching process and then oxidized.
After winding the anode foil 1 made of aluminum foil and the cathode foil 3 formed by etching the aluminum foil through the electrolytic paper 4A, the electrolytic foil 4A is carbonized by high-temperature treatment. The capacitor element 12 or 12A is manufactured by any of the methods described above, the solid organic conductive material 2 is formed between the dielectric oxide film 11 and the cathode foil 3, and the solid organic conductive material 2 is impregnated with the electrolytic solution 10 to form the solid organic conductive material 2. By swelling and infiltrating into the conductive material 2, the capacitor element 12
Or 12A is comprised. This capacitor element 12,
1A is housed in a bottomed cylindrical aluminum metal case 8 as shown in FIG. 1 (a), and the open ends of this aluminum metal case 8 are sealed by a sealing member 7 made of rubber. The external lead-out anode lead 5 and the cathode lead 6 derived from each of the above are sealed so as to penetrate the sealing member 7, and a metal case 8
Is designed to cover the side surface of the vehicle.

FIGS. 2 (a) to 2 (g) show a manufacturing process for collectively manufacturing the anode foil 1 for an electrolytic capacitor of the present invention. First, as shown in FIG. Then, an oxidizing treatment is performed on an etching foil 22 (FIG. 2B) obtained by etching the aluminum foil 21 to produce the anode foil 1 on which the dielectric oxide film 11 is formed (FIG. 2).
(C)). Subsequently, the anode foil 1 is impregnated with a solution 23 containing a polymerizable monomer capable of forming a conductive polymer layer as shown in FIG. By heating (including drying) using the heating furnace 24 as shown in e), the anode foil 1 on the surface of which the solid organic conductive material 2 is formed as shown in FIG. Subsequently, as shown in FIG. 2 (g), the cathode element 3 formed by etching the anode foil 1 and the aluminum foil 21 configured as described above is wound around the separator 4 so that the capacitor element 12 is formed. What constitutes.
The subsequent steps are the same as those in the above-described manufacturing method. The capacitor element 12 is housed in the bottomed cylindrical metal case 8 together with the electrolytic solution 10, and the open end of the metal case 8 is closed by the sealing member 7 to form the anode foil 1. And an anode lead 5 and a cathode lead 6 for external lead out from each of the cathode foil 3 are sealed so as to penetrate the sealing member 7, and the outer tube 9 covers the side surface of the metal case 8. It is.

Next, the electrolytic solution used for the electrolytic capacitor of the present invention will be specifically described. As a solvent for the electrolytic solution of the electrolytic capacitor of the present invention, γ-butyrolactone and / or ethylene glycol (boiling points of 200 ° C. or more), which are electrochemically stable and swellable in an organic conductive material, are used as main solvents. It is desirable that Also,
In addition to this, with the aim of improving low temperature characteristics and withstand voltage,
Other organic solvents compatible with γ-butyrolactone and / or ethylene glycol may be mixed as a secondary solvent, but the secondary solvent does not need to be an organic solvent capable of swelling the organic conductive material.

As the secondary solvent, in addition to the above-mentioned organic solvent having a boiling point of 200 ° C. or higher, a polyhydric alcohol solvent; propylene glycol, diethylene glycol, 1,4-butanediol, polyoxyalkylene polyol, lactone solvent; Valerolactone, δ-valerolactone,
3-ethyl-1,3-oxazolidin-2-one, water,
Amide solvents: N-methylformamide, N, N-dimethylformamide, N-methylacetamide, ether solvents: methylal, 1,2-dimethoxyethane, 1-
Ethoxy-2-methoxyethane, 1,2-diethoxyethane, nitrile solvents; acetonitrile, 3-methoxypropionitrile, furan solvents; 2,5-dimethoxytetrahydrofuran, 2-imidazolidinone solvents;
A single solvent of 1,3-dimethyl-2-imidazolidinone or a mixed solvent of two or more thereof is exemplified.

In the case of a mixed solvent system, the mixing ratio of the solvent is 2
The solvent having a boiling point of less than 200 ° C. is desirably 40 parts or less based on 100 parts of the solvent having a temperature of 00 ° C. or more. Boiling point 200 ° C
If the content of the solvent less than 40 parts exceeds 40 parts, the heat resistance at the time of forming an electrolytic capacitor for surface mounting is lowered, and the occurrence rate of defective soldering is undesirably increased.

Examples of the tertiary amine used in the electrolyte of the present invention include trialkylamines [trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl n-propylamine, dimethylisopropylamine, methylethyl n-propylamine, Methylethyl isopropylamine, diethyl n-propylamine, diethyl isopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), phenyl group-containing amine [dimethylphenylamine, methylethylphenylamine , Diethylphenylamine, etc.].

Of these, preferred are trialkylamines having high conductivity, and more preferred are trimethylamine and dimethylethylamine which can provide capacitors having high conductivity and excellent impedance performance.
One or more selected from the group consisting of methyldiethylamine and triethylamine.

Examples of the compound having an alkyl-substituted amidine group used in the electrolyte of the present invention include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). Specifically, 1,8-diazabicyclo [5,4,0] undecene-7 and 1,5-diazabicyclo [4,3,0] nonene-5 capable of providing a capacitor having high conductivity and excellent impedance performance. , 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1
-Methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2- (3'heptyl) imidazoline, 1-methyl-2-dodecylimidazoline ,
1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, 1-methylbenzimidazole are preferred.

Examples of the quaternary salt of the compound having an alkyl-substituted amidine group used in the electrolyte of the present invention include those having 1 carbon atom.
Imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with alkyl groups or arylalkyl groups of Nos. 1 to 11; Specifically, it is possible to provide an electrolytic capacitor having high heat resistance, high conductivity, and excellent long-term stability of impedance performance.
8-diazabicyclo [5,4,0] undecene-7,1
-Methyl-1,5-diazabicyclo [4,3,0] nonene-5,1,2,3-trimethylimidazolinium,
1,2,3,4-tetramethylimidazolinium, 1,
2-dimethyl-3-ethyl-imidazolinium, 1,
3,4-trimethyl-2-ethylimidazolinium,
1,3-dimethyl-2-heptylimidazolinium,
1,3-dimethyl-2-(-3'heptyl) imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrim Didium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, 1,3-
Dimethylbenzimidazolium is preferred.

Examples of the organic acid used in the electrolyte of the present invention include polycarboxylic acids (divalent to tetravalent): aliphatic polycarboxylic acids [saturated polycarboxylic acids such as oxalic acid, malonic acid,
Succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid: unsaturated polycarboxylic acid Aromatic polycarboxylic acids, such as phthalic acid, isophthalic acid, terephthalic acid,
Trimellitic acid, pyromellitic acid; alicyclic polycarboxylic acids [eg, cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.], hexahydrophthalic acid; alkyl (carbon Formulas 1-3) or nitro substituents, such as citraconic acid, dimethylmaleic acid, nitrophthalic acid (3-nitrophthalic acid, 4-nitrophthalic acid); and sulfur-containing polycarboxylic acids, such as thiopropionic acid; monocarboxylic acids; Monocarboxylic acids (1 to 30 carbon atoms) [saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, Stearic acid, behenic acid: unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid , Oleic acid]; aromatic monocarboxylic acids such as benzoic acid, o- nitrobenzoic acid, p
-Nitrobenzoic acid, cinnamic acid, naphthoic acid; oxycarboxylic acids such as salicylic acid, mandelic acid, resorcinic acid, etc. Among these, preferred are maleic acid, phthalic acid having high conductivity and being thermally stable. Acid, cyclohexanecarboxylic acid, cyclohexene-1,2-dicarboxylic acid,
Cyclohexene-1,2-dicarboxylic acid, adipic acid,
It is benzoic acid.

The ratio between the organic acid and the base constituting the electrolytic solution is usually 4 to 11, preferably 6 to 11, as the pH of the electrolytic solution.
9 Outside this range, the spark voltage of the electrolyte (withstand voltage)
Is undesirably reduced.

As the electrolyte salt, electrochemically stable organic carboxylic acids; maleic acid, phthalic acid, cyclohexanecarboxylic acid, cyclohexene-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, adipic acid, benzoic acid It is desirable to use a quaternary salt of a compound having an alkyl-substituted amidine group of an acid.

Various additives may be added to the electrolytic solution of the electrolytic capacitor of the present invention, if necessary. Additives include phosphorus compounds [phosphoric acid, phosphate esters, etc.], boric acid compounds [boric acid, complex compounds of boric acid and polysaccharides (mannitol, sorbite, etc.), boric acid and polyhydric alcohols (ethylene Glycol, glycerin and the like), nitro compounds [o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol,
m-nitrophenol, p-nitrophenol, p-nitroacetophenone, etc.]. In the case of aluminum electrolytic capacitors, the mixing of these additives can improve the reparability of the aluminum oxide film.
As a result, an electrolytic capacitor having a high withstand voltage can be easily formed, which is preferable.

The terminal rod of the electrolytic capacitor of the present invention may be subjected to anticorrosion treatment. By subjecting the rod-shaped body to anticorrosion treatment, the electrolysis current can be suppressed, and the sealing performance can be further improved. The anticorrosion treatment on the rod-shaped body is desirably performed on both the anode and cathode terminals, but may be performed on only one of the terminals. In addition, as means of the anticorrosion treatment, anodic oxidation treatment in an aqueous solution, application and sintering of a metal alkoxide, and application and sintering of a metal oxide colloid solution (colloidal solution of silicon dioxide and titanium dioxide) are simple. Is preferable.

The sealing member 7 is an elastic material obtained by adding 0.5 to 20 parts of a peroxide or an alkylphenol formalin resin as a vulcanizing agent to a butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene. The body is desirable. Further, in a vulcanization method using a vulcanizing agent other than a peroxide or an alkylphenol formalin resin (for example, sulfur vulcanization), the rubber elasticity is significantly reduced when left for a long time at high temperature and high humidity. This is not preferable because the organic conductive material may be oxidatively degraded due to invasion of water from the outside.

Next, specific embodiments of the present invention will be described, but the present invention is not limited to these embodiments. Hereinafter, all parts are by weight.

The compositions of the electrolytes used in the embodiments of the present invention and the comparative examples are as follows. In addition, pH (pH is defined by the following formula: pH = as a measure of the hydrogen ion concentration in the aqueous solution of the base of the electrolyte or the hydroxide of the base.
-Log [hydrogen ion concentration]. Therefore, when the pH is 13 or less, it means that the hydrogen ion concentration is 1.0 × 10 ⁻¹³ mol / dm ³ or more. ) Are also shown as annotations. Also, an aluminum conversion foil having a dielectric oxide film formed on the surface thereof at a voltage of 500 V was treated with these electrolytic solutions (temperature 30).
° C), and the spark generation voltage (meaning the withstand voltage of the electrolyte) and the conductivity (measured at a temperature of 30 ° C.) of the electrolytic solution observed when the constant current-voltage is increased at a constant current of 2.0 mA / cm ^2. ℃)
Are also shown.

Electrolyte solution A; γ-butyrolactone (100 parts) Mono 1,2,3,4-tetramethylimidazolinium phthalate (30 parts) [Note: pH = 11.2] o-Nitrobenzoic acid (1 Parts), monobutyl phosphate (1 part) boric acid (2 parts), mannitol (2 parts) A mixture of the above compounds and dissolved. Spark voltage is 85V
And the conductivity was 9.0 mS / cm.

Electrolyte B; γ-butyrolactone (50 parts), ethylene glycol (50 parts) trimethylammonium maleate (5 parts) [Note: pH = 9.5] Triethylamine hydrogen phthalate (5 parts) [Note: pH = 9.5] diammonium adipate (3 parts) [note: pH = 9.1] boric acid (0.5 part), p-nitrobenzoic acid (1 part), phosphoric acid (0.5 part) Compounds mixed and dissolved. Spark voltage is 180
V and the conductivity was 3.3 mS / cm.

Electrolyte C: ethylene glycol (70 parts), glycerin (30 parts) diammonium adipate (15 parts) [Note: pH = 9.1] 1,6-decanedicarboxylic acid (1 part) [Note: pH = 9.1] 1,7-octanedicarboxylic acid (1 part) [Note: pH = 9.1] o-Nitrophenol (1 part) Ammonium hypophosphite (1 part) [Note: pH = 9.1] 1] A compound obtained by mixing and dissolving the above compounds. Spark voltage is 340
V and the conductivity was 0.9 mS / cm.

Electrolyte solution D; γ-butyrolactone (100 parts) Tetramethylammonium phthalate (40 parts) [Note: pH = 13.2] A solution obtained by mixing and dissolving the above compounds. Spark voltage is 79V
And the conductivity was 11.5 mS / cm.

The sealing members of butyl rubber used in the embodiments of the present invention and the comparative examples are as follows.

Sealing member A [vulcanization with peroxide]: 30 parts of a butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene, 20 parts of carbon,
A vulcanized product obtained by adding 2 parts of dicumyl peroxide, which is a peroxide, as a vulcanizing agent to 50 parts of an inorganic filler. The hardness of the sealing member after molding was measured at the surface of the side in contact with the capacitor element between the two rubber holes for penetrating the lead and the surface of the portion in contact with the lead wire surface inside the rubber hole. Rubber hardness unit), each 67
IRHD and 66IRHD.

Sealing member B [vulcanization with resin]; 30 parts of butyl rubber polymer composed of a copolymer of isobutylene and isoprene, 20 parts of carbon, and 50 parts of inorganic filler; Vulcanized and molded by adding parts. The hardness of the sealing member after molding was measured at the surface of the side in contact with the capacitor element between the two rubber holes for penetrating the lead and the surface of the portion in contact with the lead wire surface inside the rubber hole. The rubber hardness unit was 77 IRHD and 76 IRHD, respectively.

(Embodiment 1) A wound type in which electrolytic paper (density 0.55 g / cm ³ , thickness 50 μm) containing manila hemp fiber is interposed between an anode aluminum foil and a cathode aluminum foil. After carbonizing the electrolytic paper by leaving the aluminum electrolytic capacitor element at a temperature of 300 ° C. for 30 minutes, the capacitor element is immersed in a water-ethanol solution containing ethylenedioxythiophene and ferric sulfate, pulled up, and dried and polymerized. The step of (at 105 ° C. for 10 minutes) was repeated 10 times to form a solid organic conductive material layer made of chemically polymerized polyethylene dioxythiophene on the electrode foil and between the electrode foils, and then the capacitor element was washed with water and dried. Thereafter, the capacitor element was impregnated with the electrolytic solution A to obtain an aluminum electrolytic capacitor element having a rated voltage of 50 V and a capacitance of 390 μF. After encapsulating this capacitor element together with the sealing member A in an aluminum metal case, the opening was sealed by curling to form an aluminum electrolytic capacitor (size: φ13 mm × L).
20 mm).

(Embodiment 2) A glass fiber non-woven fabric (density 0.13 g / cm ³ , thickness 50 μm), an anode aluminum foil and a cathode aluminum foil are immersed in a water-ethanol solution containing pyrrole and ammonium persulfate, respectively.
The process of dry polymerization (at 105 ° C. for 10 minutes) and drying was repeated three times to form a chemically polymerized polypyrrole, followed by washing and drying to form a separator and a chemically polymerized polypyrrole on the surface, which were made conductive by the chemically polymerized polypyrrole. An anode aluminum foil and a cathode aluminum foil were prepared. Thereafter, an anode aluminum foil and a cathode aluminum foil each having a chemically polymerized polypyrrole formed on the surface thereof are wound through the conductive separator to obtain a capacitor element, which is further dissolved in a 10% by weight soluble sulfonated polyaniline. By immersing in a solution, impregnating under reduced pressure, pulling up, and drying, a dry residue sulfonated polyaniline is formed between an anode aluminum foil and a cathode aluminum foil having a chemically polymerized polypyrrole formed on the surface, thereby strengthening electrical bonding between the electrode foils. Was. Further, an electrolytic solution A is added to this capacitor element.
To obtain an aluminum electrolytic capacitor element having a rated voltage of 50 V and a capacitance of 390 μF. After encapsulating this capacitor element in an aluminum metal case together with the sealing member A, the opening was sealed by curling to form an aluminum electrolytic capacitor (size: φ13 m).
mx L20mm).

(Embodiment 3) A glass fiber nonwoven fabric (density 0.13 g / cm ³ , thickness 50 μm), an anode aluminum foil and a cathode aluminum foil, respectively,
After applying the 8,8, tetracyanoquinodimethane complex,
A separator made conductive by cooling with a 7,7,8,8, tetracyanoquinodimethane complex; and
An anode aluminum foil and a cathode aluminum foil each having a 7,8,8, tetracyanoquinodimethane complex formed on its surface were prepared. Thereafter, a capacitor element is obtained by winding an anode aluminum foil and a cathode aluminum foil each having a 7,7,8,8, tetracyanoquinodimethane complex formed on the surface thereof through the conductive separator. Further immersion in a solution of a soluble sulfonated polyaniline having a concentration of 10% by weight, impregnation under reduced pressure, pulling-up, drying at 7,7,8,8, tetracyanoquinodimethane complex at a temperature equal to or lower than the melting point thereof, , 7,8,8,
A tetracyanoquinodimethane complex was formed between the anode aluminum foil and the cathode aluminum foil formed on the surface to enhance the electrical connection between the electrode foils. Further, this capacitor element is impregnated with the electrolytic solution A, and has a rated voltage of 50 V and a capacitance of 39 V.
An aluminum electrolytic capacitor element of 0 μF was obtained. After sealing this capacitor element together with the sealing member A in a metal case made of aluminum, the opening was sealed by curling to form an aluminum electrolytic capacitor (size: φ13 mm × L20 mm).

(Embodiment 4) Embodiment 1 of the present invention is the same as Embodiment 1 except that electrolytic solution B is used as the electrolytic solution.
Same as.

(Embodiment 5) Embodiment 1 of the present invention is the same as Embodiment 1 except that electrolytic solution C is used as the electrolytic solution.
Same as.

(Embodiment 6) Embodiment 1 of the present invention is different from Embodiment 1 in that electrolyte D is used as the electrolyte.
Same as.

(Embodiment 7) In Embodiment 1 of the present invention, except that the sealing material B is used as the sealing material.
Same as.

(Embodiment 8) Embodiment 1 of the present invention is the same as Embodiment 1 except that pyrrole is used instead of ethylenedioxythiophene.

(Embodiment 9) Embodiment 9 of the present invention is the same as Embodiment 1 except that aniline is used instead of ethylenedioxythiophene.

(Embodiment 10) Embodiment 1 of the present invention
Wherein a mixture of iron p-toluenesulfonate and iron dodecylbenzenesulfonate is used in place of ferric sulfate,
Embodiment 1 is the same as Embodiment 1 except that a water-methanol solution is used instead of the water-ethanol solution.

(Embodiment 11) Embodiment 1 of the present invention
, Except that a mixture of ammonium persulfate and aqueous hydrogen peroxide was used instead of ferric sulfate.

Comparative Example 1 A capacitor element was formed by winding electrolytic paper (density 0.55 g / cm ³ , thickness 50 μm) containing manila hemp fiber between the anode aluminum foil and the cathode aluminum foil. I got afterwards,
This capacitor element is impregnated with the electrolytic solution A and has a rated voltage of 5
An aluminum electrolytic capacitor element having a 0 V electrostatic capacity of 390 μF was obtained. After sealing this capacitor element together with the sealing member A in a metal case made of aluminum, the opening was sealed by curling to form an aluminum electrolytic capacitor (size: φ13 mm × L20 mm).

(Comparative Example 2) The same operation as in the first embodiment of the present invention was carried out except that the electrolytic solution A was not impregnated.

Comparative Example 3 A capacitor element wound with electrolytic paper (density 0.55 g / cm ³ , thickness 50 μm) containing manila hemp fiber interposed between the anode aluminum foil and the cathode aluminum foil was heated at a temperature of After the electrolytic paper was carbonized by being left at 300 ° C. for 30 minutes, the element was immersed in a 7,7,8,8, tetracyanoquinodimethane complex in a molten state, impregnated under reduced pressure, and then cooled. , 7,8,
8. A tetracyanoquinodimethane complex layer was directly formed between the electrodes to obtain an aluminum electrolytic capacitor element having a rated voltage of 50 V and a capacitance of 390 μF. After encapsulating this capacitor element together with the sealing member A in an aluminum metal case, the opening was sealed by curling to form an aluminum electrolytic capacitor (size: φ13 mm × L).
20 mm).

(Comparative Example 4) A nonwoven fabric of glass fiber (density 0.13) was placed between an anode aluminum foil and a cathode aluminum foil.
g / cm ³ , thickness of 50 μm), and immersing the aluminum electrolytic capacitor element in an aqueous solution of manganese nitrate, pulling it up, and thermally decomposing it (at 300 ° C. for 10 minutes). After directly forming a manganese dioxide layer, which is an inorganic conductive material, the capacitor element is further impregnated with an electrolytic solution A, and a rated voltage of 50 V and a capacitance of 3
A 90 μF aluminum electrolytic capacitor element was obtained. After sealing this capacitor element together with the sealing member A in a metal case made of aluminum, the opening was sealed by curling to form an aluminum electrolytic capacitor (size: φ13 mm × L20 mm).

Comparative Example 5 The procedure of Comparative Example 1 was the same as that of Comparative Example 1, except that a carbon cloth woven with carbon fibers was used instead of the electrolytic paper.

Comparative Example 6 The procedure of Comparative Example 1 was repeated except that a glass fiber nonwoven fabric coated with water-dispersed colloidal graphite was used instead of the electrolytic paper.

Table 1 shows the aluminum electrolytic capacitors according to Embodiments 1 to 11 of the present invention and Comparative Examples 1 to 6.
The initial characteristics (capacitance, impedance, leakage current value, and the number of short-circuit occurrences (defectives) during the aging process are compared.

In each case, the number of test pieces was 20, and the initial characteristics were shown by their average values (excluding short-circuited products).

[0067]

[Table 1]

As is clear from Table 1, the aluminum electrolytic capacitor constituted by using only the electrolytic solution of Comparative Example 1 has a remarkably large impedance as compared with Embodiments 1 to 11 of the present invention.

In the aluminum electrolytic capacitor of Comparative Example 5 in which a carbon cloth woven with carbon fibers was used as a means for making the separator conductive and the resistance was reduced, the impedance was improved as compared with Comparative Example 1, but the present invention was improved. It can be seen that the impedance is large as compared with the first to eleventh embodiments.

The aluminum electrolytic capacitor having only the conductive polymer (polyethylene dioxythiophene layer) of Comparative Example 2 and having no electrolytic solution, or the organic semiconductor (7,
(7,8,8, tetracyanoquinodimethane complex layer) only and no electrolytic solution, or water dispersion type colloidal graphite is applied to the separator to make the separator of Comparative Example 6 conductive. In the case of the aluminum electrolytic capacitor, the temperature is 85 ° C and the DC voltage is 63V.
All short-circuits (short-circuits between the electrodes due to insufficient withstand voltage) occurred during the aging treatment of applying.

An aluminum electrolytic capacitor using manganese dioxide, which is a solid inorganic conductive material, in place of the solid organic conductive material of Comparative Example 4 has good impedance, but is an organic electrolytic material because the conductive material is inorganic. Since the liquid was not easily diffused and the repairability of the dielectric oxide film could not be sufficiently secured, a short-circuit occurred slightly during aging.

As described above, the electrolytic capacitor of the present invention can provide an electrolytic capacitor having excellent impedance characteristics, leakage current and reliability and high withstand voltage in a simple process. Among the embodiments of the present invention, in the sixth embodiment of the present invention using the electrolytic solution D, the spark generation voltage of the electrolytic solution is 80 V or less, the withstand voltage is not sufficient, and the occurrence of a short circuit during aging is reduced. Although not provided, the leakage current value tends to be higher than in the other embodiments. In order to sufficiently exhibit the effects of the present invention in terms of withstand voltage and leakage current, it is desirable, but not essential, that the spark generation voltage of the electrolyte be as high as 80 V or more.

Further, among the embodiments of the present invention, in the fifth embodiment of the present invention using electrolytic solution C, since the conductivity of the electrolytic solution is less than 1.0 mS / cm, the conductivity is not sufficient. However, the impedance tends to be higher as compared with the other embodiments. In order to sufficiently exhibit the effect of the present invention in terms of impedance performance, it is desirable, but not essential, that the conductivity of the electrolyte be as high as 1.0 mS / cm or more.

Table 2 shows that the aluminum electrolytic capacitors according to Embodiments 1 to 11 of the present invention were stored at a temperature of 60 ° C. and a relative humidity of 9%.
10 tests to continuously apply a rated voltage of 50 V in 5% RH
It is the result of observing the state of the sealing member surface after performing 00h. In each case, the test number is 20 pieces.

[0075]

[Table 2]

As is clear from (Table 2), no remarkable abnormality was observed in any of the embodiments.
In the sixth embodiment using the electrolyte solution D, since the electrolyte base is a strongly basic base having a hydrogen ion concentration of less than 1.0 × 10 ⁻¹³ mol / dm ^3, it can be used in a high-temperature / high-humidity complex environment. In the test for a long time, the sealing member (sealing portion) is easily damaged by the influence of the strong basic base.
The more the liquid leaked. Although it is not an essential condition for sufficiently exhibiting the effect of the present invention in terms of reliability, the concentration of the base or the hydroxide of the base in the base constituting the electrolyte is 1% by weight and the measurement temperature is 30%.
It is desirable to select one having a hydrogen ion concentration of 1.0 × 10 ⁻¹³ mol / dm ³ or more in an aqueous solution of a base or a hydroxide of a base at a temperature of ° C.

Next, the methods of Embodiments 1 to 11 of the present invention and Comparative Examples 2 to 3 were similarly used again to obtain an aluminum electrolytic capacitor element having a rated voltage of 6.3 V and a capacitance of 1000 μF. After encapsulating this capacitor element in an aluminum metal case together with the sealing member A, the opening is sealed by curling treatment, and a resin seat plate made of polyphenylene sulfide is attached to form a vertical surface mount type aluminum electrolytic capacitor. (Size: φ10m
mx L10 mm). The surface-mount type aluminum electrolytic capacitor thus configured is connected to a glass epoxy substrate (thickness 2).
mm) using cream solder (Sn-Pb eutectic composition) and passed through a reflow furnace that uses both infrared and hot air (peak temperature 240 ° C., exposure time to 200 ° C. or more 50 hours).
Second), and a heat-resistance test was performed (20 test pieces).

As a result, the surface mount type aluminum electrolytic capacitor constructed by the method of the first to eleventh embodiments of the present invention has a boiling point of 20% added to the solid organic conductive material as an electrolyte.
Because an electrolytic solution composed of an organic solvent at 0 ° C. or higher is used,
As a result of suppressing an increase in the pressure inside the capacitor due to the water adsorbed on the member, problems such as mounting failure due to popping out of the sealing member and swelling of the sealing member surface did not occur. on the other hand,
In the surface-mount type aluminum electrolytic capacitor formed by the method of Comparative Examples 2 and 3 using only the solid organic conductive material as the electrolyte, the pressure inside the capacitor was remarkably increased due to the adsorbed water, so that all 20 sealing members jumped out. . As is apparent from the results, the surface-mount type aluminum electrolytic capacitor formed by the method of the embodiment of the present invention is:
By providing an electrolytic solution comprising an organic solvent having a boiling point of 200 ° C. or higher in addition to the solid organic conductive material, heat resistance during mounting can be improved.

[0079]

As described above, the electrolytic capacitor according to the present invention can provide an electrolytic capacitor having excellent impedance characteristics, leakage current, and high reliability, and having a high industrial value. It is.

[Brief description of the drawings]

FIG. 1A is a partial cross-sectional perspective view showing a configuration of an electrolytic capacitor according to a first embodiment of the present invention. FIG. 1B is a conceptual diagram in which main parts of the capacitor element are enlarged.

FIGS. 2A to 2G are manufacturing process diagrams for manufacturing an anode foil of the electrolytic capacitor according to the embodiment;

[Explanation of symbols]

 Reference Signs List 1 anode foil 2 solid organic conductive material 3 cathode foil 5 anode lead 6 cathode lead 7 sealing member 8 metal case 9 outer tube 10 electrolytic solution 11 dielectric oxide film 21 aluminum foil 22 etching foil 23 solution containing polymerizable monomer 24 heating Furnace

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Shigeyoshi Iwamoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] An anode foil made of a valve metal having a dielectric oxide film formed on a surface thereof; a cathode foil; a capacitor element made of a solid organic conductive material provided between the anode foil and the cathode foil; An electrolytic capacitor comprising a bottomed cylindrical metal case for accommodating the capacitor element together with a driving electrolyte, and a sealing member for sealing an opening of the metal case. 2. The electrolytic capacitor according to claim 1, wherein the solid organic conductive material is made of one or both of an organic semiconductor and a conductive polymer. 3. The electrolytic capacitor according to claim 2, wherein the organic semiconductor comprises a 7,7,8,8, tetracyanoquinodimethane complex and a derivative thereof. 4. The conductive polymer is pyrrole, aniline, thiophene, ethylenedioxythiophene, sulfonated aniline, sulfonated pyrrole, sulfonated thiophene,
3. The electrolytic capacitor according to claim 2, wherein the electrolytic capacitor is at least one selected from sulfonated ethylenedioxythiophene and a polymer of these derivatives. 5. The conductive polymer is at least one selected from a liquid-phase chemical polymerization composition, a gas-phase polymerization composition, a liquid-phase-electropolymerization composition, and a dry residue polymer of a soluble polymer solution. 5. The electrolytic capacitor according to 4. 6. A dried product obtained by drying a polypyrrole, polyethylene dioxythiophene, polyaniline formed by chemical polymerization of a conductive polymer, a polypyrrole formed by electrolytic polymerization, polyethylene dioxythiophene, polyaniline, and a soluble polyaniline solution. 5. At least one selected from residual sulfonated polyaniline.
Or the electrolytic capacitor according to 5. 7. The driving electrolyte according to claim 1, wherein an organic acid salt and an inorganic acid salt are dissolved in an organic solvent capable of being swelled by being immersed in a solid organic conductive material. The electrolytic capacitor as described. 8. An electrolyte to be dissolved in a driving electrolyte is a base constituting the electrolyte, wherein the concentration of the base or the hydroxide of the base is 1% by weight and the base or the hydroxylation of the base when the measurement temperature is 30 ° C. electrolytic capacitor according to claim 7 hydrogen ion concentration is 1.0 × 10 ^{-1 3} mol / dm ³ or more in an aqueous solution of the object. 9. The method according to claim 8, wherein the base constituting the electrolyte is at least one selected from a compound having an alkyl-substituted amidine group, a quaternary salt of a compound having an alkyl-substituted amidine group, a tertiary amine, and ammonium. Electrolytic capacitor. 10. A quaternary salt of a compound having an alkyl-substituted amidine group is selected from imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms. The electrolytic capacitor according to claim 9, wherein the electrolytic capacitor is at least one type. 11. A quaternary salt of a compound having an alkyl-substituted amidine group is 1-methyl-1,8-diazabicyclo [5,4,0] undecene-7,1-methyl-1,5-
Diazabicyclo [4,3,0] nonene-5,1,2,3
-Trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2
-Ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(-
3 'heptyl) imidazolinium, 1,3-dimethyl-
2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,
The electrolytic capacitor according to claim 10, wherein the electrolytic capacitor is at least one selected from 3-dimethylimidazolium, 1-methyl-3-ethyl-imidazolium, and 1,3-dimethylbenzimidazolium. 12. The boiling point of the solvent of the driving electrolyte is 200 ° C.
The electrolytic capacitor according to claim 11, wherein the electric conductivity of the driving electrolyte at a measurement temperature of 30 ° C is 1.0 mS / cm or more, and the spark generation voltage is 80 V or more.